Gauges of all sorts indicating the amount of fuel, temperature of an engine, oil pressure, speed and indicators of other various parameters are commonly mounted to an instrument panel of a variety of vehicles, including but not limited to automobiles, boats or airplanes. A typical method of mounting said gauges requires an annular gauge housing with a thin flange at one end and a cylindrical or conical body that is placed into a hole in a instrument panel. A U-shaped or cup shaped mounting bracket is attached to the housing from the backside of the instrument panel sandwiching the instrument panel between the gauge housing flange and the mounting bracket. The mounting bracket can be attached to the gauge housing in a variety of ways. The most common method of mounting a gauge is by use of mounting studs assembled to the gauge housing. The mounting bracket is provided with holes through which the mounting studs pass. The gauge is inserted from the front through the hole in the panel and the mounting bracket is passed over the mounting studs from the backside of the panel. Mounting nuts are screwed onto the studs and tightened against the mounting bracket to sandwich the instrument panel between the gauge housing flange and the mounting bracket.
A second method of mounting a gauge comprises a screw thread on the outer wall of the gauge housing and a corresponding screw thread on the inner wall of the mounting bracket. The gauge is inserted through the opening in the instrument panel and the bracket is screwed onto the gauge housing from the backside to sandwich the panel between the gauge housing and bracket. In order to accommodate various thickness panels extending threading on either the mounting studs or gauge housing is required. This results in an ergonomically difficult and time-consuming operation.
A third typical method of mounting consists of using a smooth wall gauge housing and an internally toothed mounting bracket. This mounting bracket has tapered internal threads, and a separate metal ring that travels in this thread. The separate metal ring has protrusions similar to saw teeth. The gauge is inserted through the opening in the instrument panel as with the previous methods, and the bracket is pushed from the rear around the gauge housing and tight up against the instrument panel. Twisting the bracket in a clockwise manner engages the internally captive toothed ring against the gauge housing, and further tightening causes this member to draw the gauge housing tight up against the instrument panel. This method produces a number of stress riser points on the exterior wall of the gauge housing where the teeth of the metal toothed ring component contact the housing wall. Additionally, the tapered threads of the bracket place a significant inward radial hoop stress on the gauge housing and the mechanical advantage of the screw thread places a large axial load on the thin flange of the gauge housing. The combination of stress risers and applied stresses can potentially cause the gauge housing to fail at the flange.
A fourth method of mounting gauges to instrument panels uses a specially molded plastic housing that has four flexible flaps extending tangentially from the round base portion, the flaps being free to flex radially inward towards the base portion to permit passage of the flap through the opening in a panel. Each of the flaps has a stepped edge surface facing the flange, the axial spacing between a tread portion of each step and the flange decreasing going from a radially outermost step to a radially innermost step, and the tread portion of each step defining a respective panel abutting surface for abutting the rear side of the panel. The relatively large distance between the tread portions of each step limits this method of mounting limits to a specific dimensional thickness that corresponds to the corresponding dimensions of the tread steps. If the panel thickness does not correspond to the dimensions of the tread portions the gauge housing is not tightly secured to the panel resulting in the gauge being allowed to move excessively when the gauge is placed in vibration.